In a machine tool such as a lathe, a rotary tool holder structure (i.e., a structure having a turret tool holder) is well known, and is adapted to support a plurality of tools, select a desired tool by rotational indexing motion, and locate the tool at a processing operation position, in order to facilitate automation and speeding up of the processing operation. For example, a turret tool holder, used in an automatic lathe, such as a NC lathe, generally has a toolslide arranged on a machine base and opposite a main spindle, a support arranged on the toolslide movable along a given coordinate axis, and a turret rotatably arranged on the support and adapted to hold a plurality of tools around a rotational axis at specified intervals.
In such a turret tool holder, after the turret carries out rotational indexing, it is necessary to firmly fix the turret on the support when a workpiece is processed by the selected tool. Therefore, generally, the turret tool holder device has engaging means adapted to lock the turret to each of the indexing positions on the support. For example, Patent Document 1 discloses a turret tool holder device having an engage/disengage drive mechanism adapted to statically hold or release a turret at an indexing position on a support and release, wherein drive force by the drive mechanism can be transmitted to the turret by means of a lever mechanism.